This invention relates to color electrophotographic apparatus, and more particularly it is concerned with a novel color electrophotographic apparatus of the type wherein an electrophotographic photoreceptor is moved in reciprocatory movements between an exposing station and a transfer printing station, and an electrostatic latent image is formed on the photoreceptor and printed on a transfer printing sheet and developed each time the photoreceptor makes one reciprocating movement.
The most important thing in producing a good picture in color electrophotography is to prevent occurrence of misregistration of images when color-selective reflection and transmission filters are used for projecting images and then developing such images in a series of operations. It has hitherto been customary to use a photosensitive drum, for example, which is made to rotate continuously so that charging, exposing, developing and transfer printing may be performed during its rotation. The use of such rotary photosensitive drum has posed the problem of how to synchronize the rotation of the drum with the movement of the optical system. In order to obviate this problem, it has been necessary to use a mechanism of complex structure which has inevitably raised the cost of production.
On the other hand, in another type of color electrophotography known in the art, one photoreceptor is used and subjected to a series of charging, exposing and developing operations. In this system, charging and exposing are performed on the photoreceptor to form an electrostatic latent image on the photoreceptor on which a toner image has already been formed. This system has a disadvantage in that the sensitivity of the photoreceptor is reduced by the presence of the toner image, with the result that the electrostatic latent image formed in the next series of charging, exposing and developing operations leaves much to be desired. Another disadvantage of this system is that since a toner image is formed on the photoreceptor, it is essential that the photoreceptor be cleaned, and the cleaning of the photoreceptor leads to a short service life.